This R25 renewal application responds to PAR-16-224 for continued funding for the UCLA HIV/AIDS, Substance Abuse, and Trauma Training Program (HA-STTP). Our Program's mission is to provide training and mentorship to early career postdoctoral scholars whose focus is reducing substance abuse and transmission of HIV in underserved populations at high risk for traumatic stress and health disparities. To date, our Program has been highly successful in training a diverse, productive group of 19 Scholars and seven Affiliate Scholars. Our core curriculum will maintain focus on our core topics, with the addition in this renewal of courses on social network analysis, technology-based interventions, addiction psychiatry, and implementation science. Our Program provides a two-year course of training and mentorship to a total of 20 (five/year over four years) postdoctoral and early career scholars. Our Program is unique in its incorporation of traumatic stress as a form of dysregulation, particularly as experienced by underserved populations. These populations, particularly racial/ethnic minority populations, are disproportionately affected by HIV/AIDS and typically experience a high degree of traumatic stress. Our Specific Aims are to: (1) Advance HA-TTP Scholars' knowledge of the ways in which substance abuse, HIV/AIDS, traumatic stress, and health disparities are interconnected, particularly in underrepresented populations; (2) Provide focused, intensive mentorship to support Scholars' research interests and career trajectories in the key areas addressed by this Program; (3) Capitalize on a local and national multidisciplinary, multiracial/ethnic network of expert faculty who are committed to fostering the intellectual and professional growth of the Scholars; and (4) Evaluate the impact of the Program on Scholars' knowledge and productivity. Scholars will attend two week-long Institutes per year for two years and will receive continual, personalized career mentoring, training, and research supervision. Each cohort will be followed for the duration of the training grant, and all cohorts will come to together in the final year to share their experiences and successes. Scholars will be mentored by a UCLA-based core faculty mentor as well as a home mentor. Scholars will develop the necessary skills to pursue a productive research program in areas related to substance use, HIV/AIDS, traumatic stress, and health disparities. They will be supported in the development of competitive grant applications, including receiving a modest amount of funds to prepare preliminary studies data. The UCLA-based leadership team and core faculty include members from clinical and community psychology, medical anthropology, addiction psychiatry, public health, and social work. This Program will enhance nationwide efforts to diminish the prevalence of HIV/AIDS, substance use and traumatic stress to improve health and quality of life.